Is there a mechanism within CA Datacom/AD and CA Datacom/DB that will keep me from accidentally starting my Multi-User Facility (called MUF) more than once?
There are a number of protection and data integrity features built into version 14.0 of CA Datacom. One of these items involves the use of the SIMPLIFY feature, which provides for a protective enqueue on the CXX, and which means that each CXX and MUF needs to have a unique name. According to the CA Datacom/AD Installation Guide for version 14.0:
A unique CXX name is not only a best practice but a requirement for using the SIMPLIFY feature in CA Datacom/AD Version 14.0. To simplify naming standards, give the CA Datacom/AD MUF name and the CXX name the same value?.CA Datacom forces an enqueue action on the CXX SYSPLEX wide for CA Datacom/AD. A good practice is a unique name for all CXX names for your site. Starting with CA Datacom/AD Version 14.0, the CXX name has no default value, therefore you must determine that unique value yourself.
While the above comments come from the CA Datacom/AD Installation Guide, they apply equally to CA Datacom/DB using Simplify mode.
Once the first MUF is running, if you tried to start another one that was using the same CXX name, the second MUF would abend:
ABEND=S000 U0004 REASON=00000000
and there would be two messages that identify this problem:
DB00242E - REQUIRED ENQ NOT AVAILABLE, MUFNAME=mufname
DB00205E - MULTI-USER ERROR - 0004 MUFNAME=mufname SVC=000
From the CA Datacom/DB Message Reference Guide for Version 14.0:
REQUIRED ENQ NOT AVAILABLE, MUFNAME=mufname
This message only occurs in z/OS if the Multi-User Facility (MUF) terminates with a user 4. The message occurs because another job, or another started task, owns the MUF control ENQ that is required.
If this message is followed by a DB00205E - MULTI-USER ERROR - 004 message, this MUF may not enable because the ENQ indicates another MUF is currently executing with the same identity this MUF wants to assume.
Take action as appropriate in reaction to the message text you received.
MULTI-USER ... ERROR - nnnn .optional-text.
. . .
NOT VALID WHEN MUF UP
A function was executed that requires the Multi-User Facility to be stopped.
Before executing the function again, either wait until the Multi-User Facility has been stopped or stop it yourself using the EOJ option of the DBUTLTY COMM function or the related console command: COMM EOJ.
Therefore, if you see the DB00242E error followed by the DB00205E - MULTI-USER ERROR - 0004 error, you will know that the MUF is already running.
For more information about installing CA Datacom/AD in a SYSPLEX environment, please refer to the CA Datacom/AD Installation Guide for Version 14.0 in the section "Starting Your Product > Installation in the SYSPLEX Environment."
For more information about the Simplify feature, please refer to the CA Datacom/DB Database and System Administration Guide for Version 14.0, in the section "Introduction > Simplify Feature."
As always, please contact CA Technologies support for CA Datacom if you have further questions.